Drones sank two cargo ships and damaged a third in the exclusive economic zones of NATO member countries for the first time, killing at least two sailors. The attacks represent a notable escalation as Black Sea commercial shipping has increasingly come under attack during the Russian invasion of Ukraine, with Russia also being accused of carrying out “hybrid warfare” incidents across Europe.

The Togo-flagged cargo ship Alfa Watan sank, and the Palau-flagged cargo ship Able was set ablaze after being attacked by multiple sea and aerial drones about 80 miles (128 kilometers) off the coast of Bulgaria on October 6, according to the Associated Press. In an interview, Bulgarian Prime Minister Rumen Radev described the incidents as “an unacceptable attack in Bulgaria’s exclusive economic zone” and “a blatant violation of international law and maritime law.”